At 8.12pm on Thursday night in New York, one by one they lined up to try and destroy 20 years of hard work. First Iran, then North Korea and then Syria.

This was supposed to be the moment the United Nations took a truly historic step and adopted an Arms Trade Treaty.

No longer would there be a hiding place for unscrupulous individuals and states. The Treaty, if adopted, could save the lives of millions. It could stop the flow of arms into the hands of warlords, tyrants and human rights abusers. Mali, the Democratic Republic of the Congo and Sri Lanka are all examples of the horrific consequences of an unregulated arms trade.

But instead of a moment of history, I witnessed a moment of cynical opportunism.

The irony that the three countries who opposed the Treaty - Iran, North Korea and Syria - are under some form of sanctions, including arms embargoes, and have abysmal human rights records, having even used arms against their own citizens, was not lost on the vast majority of the delegates and observers present. The atrocities they have committed are precisely the type that the draft treaty was aimed to prevent.

There were delegates from all four corners of the globe shaking their heads in disappointment. The President of the Diplomatic Conference, the Australian Ambassador Peter Woolcott, tried desperately to revive consensus and took the unprecedented step of calling for further consultations, But it was all in vain. At 10.32pm, Iran spoke once more - and the trio of nations had their moment in the Sun.

But of course after 20 years of campaigning, we at Amnesty will not give up now. There actions should not be viewed as a defeat, but as a mere delay. The will was there. We will have an Arms Trade Treaty and soon.

Amnesty will be pushing for the United Nations General Assembly to approve the Treaty at a special session on Tuesday - a move proposed last night by Kenya. The Treaty may not get the consensus we had worked so hard to get, but it may still come into force if enough states can rally behind it. And it was particularly notable that the United States has put its weight behind ensuring the Treaty becomes a reality.

There is too much to lose. Indeed it was an Amnesty arms expert that first mooted the idea of a Treaty.

In those early days, it was Amnesty, Saferworld, the World Development Movement and the British-American Security Information Council that blazed a trail for the Treaty.

That led to the "State of the World Forum" in San Francisco in October 1996, convened by the former Costa Rican President and Nobel Peace Prize Winner Óscar Arias. It was there that the campaign truly began.

Amnesty members have been at the forefront of the campaign they helped launch the Control Arms campaign in October 2003 with Oxfam and the International Action Network on Small Arms (IANSA) in more than 100 countries.

Amnesty members here in the UK have been tireless in their efforts. They have repeatedly lobbied parliamentarians here to get the UK government to deliver an effective and worthwhile Treaty with human rights at its heart.

It has been a long battle and Amnesty will not give up. There has been such great progress over the years and even over the last few days there have been marked improvements.

Amnesty feared that the final draft of the Treaty would not be strong enough and would contain too many loopholes.

Before Wednesday's second draft, we were concerned that the Treaty would not be worthwhile. The first draft had huge gaps in it.

The treaty needed to include the Golden Rule. A Rule that would have assessed any proposed arms transfer to see if there is a substantial risk they would be used to commit or facilitate serious violations of human rights. If there is such a risk, the transfer would not take place. That rule was there.

Then there is the need for transparency. The world needs to know about the movement of arms. For it be effective, there needs to be a process to see where the weapons are going. That process was there.

And finally, as time moves on new weapons will be developed. The Treaty needed to be adaptable to account for these developments. It needs to be future-proofed and not frozen in time. That ability was there too.

It was not perfect. We were concerned that the scope of the treaty and that the range of equipment covered was far too narrow. But overall it was a good Treaty. It was one we approved of. So to see Iran, then North Korea, then Syria block it was heartbreaking.

It now all rests on Tuesday. And for all the years of hard-work that Amnesty members have put in, I sincerely hope that the member states will see sense and adopt the Treaty.